<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .box {
        width: 100px;
        height: 100px;
        background-color: pink;
        position: absolute;
      }
    </style>
  </head>
  <body>
    <div class="box"></div>
    <script>
      var boxEle = document.querySelector(".box");
      boxEle.onmousedown = function (e) {
        console.log("黑色的框");
        var x = e.clientX - boxEle.offsetLeft;
        var y = e.clientY - boxEle.offsetTop;
        boxEle.onmousemove = function (e) {
          console.log("移动了");
          var xx = e.clientX;
          var sx = xx - x; // xx-(e.clientX-boxEle.offsetLeft)
          var yy = e.clientY;
          var sy = yy - y;
          // 设置left的值；
          boxEle.style.left = sx + "px";
          boxEle.style.top = sy + "px";
        };
      };
    </script>
  </body>
</html>
